1.) Slang for blowjob, or oral sex performed by females.
2.) A way of someone receiving pain for stupid thoughts or ideas by giving them a hard slap on the back of their neck.
3.) The area between your head and your shoulders.

1.) Man, that ho gave me neck the other day!
2.) We should what?!?! Boy! That's neck!
3.) He has a giraffe neck!